Late Jurassic (Tithonian)

Morrison Formation

Bone Cabin Quarry, Albany County, WY, USA

Ultra-rare 1mm mammal tooth.

Mammal.

The mammals of the Jurassic would have looked vaguely rodent-like to us though they lived at least 85 million years before the earliest true rodents appeared.  These animals belong to groups not far removed from the earliest mammals of the Late Triassic with many of them unrelated to any group even living in the Late Cretaceous.  From that you can imagine how distantly-related most of them are from any group living today.